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1985-05-08
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This document describes the use of the IBM Personal Computer
with a Kantronics interface attached for RTTY operation.
While I have designed around a specific Terminal Unit (TU),
I have attempted to keep the program generalized such that
any TU with an RS-232C interface could be adapted. The
general use of the RS-232C lines is as follows:
Transmit Data - Async data out
Receive Data - Async data in
Carier Detect - CW data in
Request to Send - Key transmitter
Data Terminal Ready - CW ID control
The Kantronics interface does not provide an RS-232C level
and also requires an external power supply. Additionally,
the RTTY transmit line requires a normal space condition
for receive to operate correctly. Based on these
considerations, I designed a special RS-232C to Kantronics
interface box. The schematic is included below. First,
just a few words about the circuit. The interface chips
used are the same as those used in the IBM PC, namely,
the 75150 line driver and the 75154 line receiver.
The 74LS00 is used to gate the Tx data signal with the
transmitter key and to invert the RTTY transmit signal.
I used two regulators to get +/-12 volts, then I cheated
(just a little). The 75154 has a regulator built into the
chip which will regulate the +12 volts down to approximately
+5 volts. In actual measurement, it's closer to +6 volts,
but I figured that it was worth the risk (for me anyway).
I used the new +5 volts from the 75154 to supply the voltage
for the 74LS00. The unused inputs of the 74LS00 are tied
to ground to keep supply current requirements to a minimum.
The recommended voltage regulators are the 7812 and the 7912
or whichever regulator is your favorite. Just be sure to
have enough filter capacitance on the input and enough heat
sink on the regulators. There is nothing worse than
intermittent problems.
_____________________
| __________ |
+-|1 |- +12v | ____________________________ CWID
+-| |- +5v---' |
`-| |- | ________________________ KEYIN
DTR ---------| |----------' | __________
Tx data -----| |-------, +--|1 |- +5v
RTS ---------| |------- ------+--| |---,
-| 75154 |- | ,-| |---+
Gnd -|__________|--, | `-| |- |
________________| `---------| |---+
| ,---------| 74LS00 |---+
| | Gnd -|__________|- |
| | `- Gnd
| |
| |_______________________________ RTTY
|
___`_____________________________________________________ DECODE
| ,
| |
| | __________
| `--|1 |- +12v
+------| |------------,
`------| 75150 |--------, |
Gnd -|__________|- -12v | |
| |
| |
Rx data -------------------------' |
CD ----------------------------------'
Computer Kantronics
Interface Interface
Note: Intersections are indicated by "+"
Non-Intersections are indicated by " "
Kantronics RS-232C Interface
The RTTY program is written primarily in BASIC for the
IBM Personal Computer. There are two routines written
in Assembly language to scroll half screens and to send
the CW ID with accurate timing. The program will run
under interpreter BASIC but performance is marginal.
The compiled BASIC version seems to perform adequately.
The program supports both BAUDOT and ASCII RTTY modes
at BAUD rates of 45.5, 50, 56.9, 74.2, and 110. The
received input can be directed to the printer or diskette
as well as to the display. During receiving operations,
a 4000 character transmit buffer can be filled from the
keyboard or diskette. There are several predefined files
which can be loaded into the transmit buffer with the stroke
of a function key. The transmit buffer can be edited
minimally by using the backspace key. Currently, only
the last line entered is erased on the screen, however,
pressing backspace will go further than the last line.
Backspacing will not go further back than the last character
sent to the Asynchronous communications code. In the transmit
mode, a date and time stamp can be sent over RTTY, as well as,
a predifined RTTY ID field. At any time during transmission
a function key can be pressed which will stop sending
characters to the Asynchronous communications routine, thus
allowing a chance to send your CW ID by pressing another
function key. Transmission of RTTY resumes when the function
key is pressed again. The program is controlled by the use
of the ten function keys on the keyboard. They are
defined as follows:
General funtion keys
F1 - KEYS = Changes the function of keys F5, F7, and F8 (toggle)
F2 - PRTR ON/OFF = Directs received data to printer (toggle)
F3 - RX FILE = Allows direction of received data to diskette
pressing a second time terminates file transfer
F4 - TX FILE = Allows specifying diskette file to be placed in the
transmit buffer, pressing a second time terminates
file transfer
F6 - RCV/XMIT = Places program in receive mode or transmit mode
Receive Mode function keys
(KEYS mode 1)
F5 - END = Terminate program
F7 - BAUD RATE = Displays/selects current baud rate (toggle)
F8 - BAUDOT/ASCII = Displays/selects current RTTY mode (toggle)
F9 - NEWLINE = Forces a carriage return during RTTY reception
F10 - CASE = Forces a shift to LETTERS during RTTY reception
(KEYS mode 2)
F5 - RESET = Restart the program
F7 - TX CQ = Read the predefined CQ file from diskette and
place in the transmit buffer
F8 - TX RY = Read the predefined RY file from diskette and
place in the transmit buffer
F9 - NEWLINE = See above
F10 - CASE = See above
Transmit Mode function keys
(KEYS mode 1)
F5 - END = Terminate program
F7 - PSE ON/OFF = Halts/starts RTTY transmission from transmit buffer
F8 - TTYID = Places the predifined RTTY ID into the transmit buffer
F9 - CW-ID = Sends the predefined CW ID in MORSE code
F10 - DT&TM = Places the current time and date in the transmit buffer
(KEYS mode 2)
F5 - RESET = Restart the program
F7 - TX CQ = Read the predefined CQ file from diskette and
place in the transmit buffer
F8 - TX RY = Read the predefined RY file from diskette and
place in the transmit buffer
F9 - CW-ID = See above
F10 - DT&TM = See above
The program is still in the development stage. One of the
limitations is that when morse code is sent, the system is
placed in a tight timing loop. In this tight loop interrupts
can still be handled, but the overall function is impaired.
For example, a character is taken from the keyboard only
between morse characters and only one character is taken.
Another limitation is the way the printer functions.
Namely, the printer buffers a line and then ties up the
system while the line is printed. Ideally, the printer
should be buffered a little better. While not a severe
limitation, the receive buffer is disabled during file name
entry. The backup feature of the transmit buffer needs to
be improved to backup past the beginning of the line.
There are probably others that time will display.
I would like to get the code written to receive morse code.
I prefer to arrive at an algorithm which will accept a
wide variety of code speeds and will allow for somewhat
sloppy sending techniques. Then the basic split screen
approach could be applied to morse code as well as RTTY.
The morse sending program should offer adjustable code
speed both character speed and word speed.
If you have further comments or suggestions feel free to
send them to
Glenn Welman
2M2/203
Boca Raton, Fl